textproduct: Albany

WHAT HAS CHANGED

Winter Storm Watches issued for northern Herkimer, Hamilton and northern Fulton County for Wednesday afternoon into Thursday due to higher snowfall amounts expected across the south facing slopes of the southwest Adirondacks.

We continue to closely monitor a winter storm for Sunday into potentially Monday. While there remains discrepancies on its storm track which will ultimately determine overall impacts in eastern NY and western New England, there is increasing confidence in two potential scenarios. See Key Message 3 for details.

KEY MESSAGES

1) Colder than normal temperatures through Wednesday with heavy lake effect snow accumulations for parts of the western Adirondacks through tonight resulting in difficult travel. Additional snow accumulations likely for areas mainly near and north of I-90 Wednesday afternoon through Friday.

2) Moderate to high confidence for dangerous cold temperatures Friday night through early next week. Extreme Cold Weather Warnings and Cold Weather Advisories will likely be needed.

3) We continue to closely monitor a winter storm passing to our south and east for Sunday into potentially Monday. Should the storm track slightly further north, light to moderate snowfall amounts are possible, especially for areas south I-90. If the storm tracks further south, light snowfall may only graze southern zones, if not miss our area completely

DISCUSSION

KEY MESSAGE 1...

High pressure building from the Southeast U.S will maintain breezy westerly winds through this afternoon across the region and with temperatures only in the single digits and teens, the wind chills or feel-like temperatures are closer to 0 and even in the negative single digits in the higher terrain areas. Meanwhile, our lake effect band off Lake Ontario is reintensifying this afternoon per the latest TYX radar reflectivities as a shortwave tracks passes through Ontario and strengthens the westerly flow fetch. Latest snowfall totals from ground truth observations and NYS mesonet sites have fallen short of initial expectations and only range 3 to 6 inches; however, with the HREF showing potential for 0.5-1 inch per hour snowfall rates through this evening, expecting an additional 2 to 4 inches before winds back to southwest directing the band northward into the North Country by 06 - 09 UTC tonight. In addition, gusty winds 20-25kts will reduce visibility, lead to blowing snow and also result in low wind chill values -5F to -15F through tonight. Will maintain the winter storm warnings and winter weather advisories in northern Herkimer and Hamilton County, respectively, but overall storm total snowfall amounts have decreased with amounts now only ranging 5 to 9 inches (highest still north of Route 28). Otherwise, temperatures tonight turn quite chilly falling into the single digits across eastern NY and western New England as winds weaken and skies clear tonight supporting radiational cooling.

After a short break tomorrow morning, chances for snow increase again tomorrow afternoon into Thursday as a clipper passing to our west strengthens southwest winds in the low and mid-levels, generating isentropic lift. As discussed in our previous discussion, local research shows this wind regime favors snow accumulations along our south-facing upslope areas in the southwest Adirondacks, northern Mohawk Valley and southern Greens leading to light to moderate snowfall. In fact, the latest HREF shows a period of 0.5 to 1 inch per hour snowfall rates tomorrow afternoon into tomorrow evening. The latest forecast amounts have increased to 5 to 9 inches in the south- facing Adirondack slopes with 2 to 4 inches along the Adirondack foothills and southern Greens. Given increased confidence for amounts exceeding 4 inches, we issued Winter Storm Watches in northern Herkimer, Hamilton and northern Fulton from 18 UTC Wed to 18 UTC Thurs. Much lighter amounts less than 1 inch elsewhere and very little from around Albany south due to downsloping. Otherwise, southerly surface winds become gusty tomorrow afternoon into the evening reaching 20-30 mph but the lower inversion heights should prevent winds from being too strong. In addition, the southerly flow should also yield slightly warmer sfc temperatures rising into the 20s.

Low and mid-level winds veer to the west-southwest late Wed night into Thursday morning as we enter into the warm sector resulting in weakening snowfall rates. Temperatures actually become rather mild on Thursday (especially compared to the previous few days) reaching into the low to mid 30s (even upper 30s to low 40s mid-Hudson Valley). However, the break from winter weather is short-lived as the main cold front pushes through between 15 and 21 UTC from northwest to southeast, leading to brief areas of light snow or snow showers resulting in light snow accumulations (mainly coating to 1"). Winds turn quite gusty behind this cold front with forecast soundings showing the mixed layer becoming quite deep supporting wind gusts reaching 30 to 40mph. The strong west-southwest winds will also generate additional lake effect snow off Lake Ontario that becomes directed into northern Herkimer and Hamilton County starting late Thursday afternoon and continues through Friday. Additional lake effect winter storm warnings and advisories will likely be needed.

KEY MESSAGE 2...

Our true Arctic cold front pushes across the region Friday afternoon as the parent trough swings through the Northeast. There continues to be good model agreement on timing, with increasing confidence in the magnitude of cold air surging in behind the front resulting in the coldest air of the winter season thus far. To put into perspective just how anomalous this cold outbreak is, we can look at the Extreme Forecast Index (EFI) which shows values ranging -0.8 and -0.9. That shows that even with respect to climatology for late January which is when we experience the coldest temperatures of the calendar year, this event is still flagged as unusual.

Northwest winds will funnel very cold air into the region with 925 - 850 hPa isotherms falling to -25 C to -30C Friday night into early Saturday and with winds staying breezy 25 - 30mph, the most dangerous wind chills of the weekend are likely Friday night into early Saturday with values in the latest forecast nearing -25F to -30F in the southwest Adirondacks and southern Greens with -5F to -15F elsewhere. Such values easily meet our cold weather advisory and extreme cold warnings so there is moderate to high confidence needing these products Fri night into early Saturday.

A 1045 hPa high builds into the Great Lakes by Saturday, weakening the sfc pressure gradient and weakening winds. While this will decrease our wind chill values, it will still be frigid as the core of the cold will be overhead resulting in daytime highs on Saturday only rising into the single digits and to near 10 degrees across eastern NY and western New England. The normal high temperature for late January is in the low to mid 30s so these temperatures are 20 degrees below normal. Temperatures remain very cold Saturday night and Sunday with overnight lows falling into the negative teens in the southern Adirondacks and southern Greens and low to mid single digits in the valley. Daytime highs Sunday should rise slightly into the single digits to mid teens. Given weakening winds during this period as high pressure builds overhead, wind chills should not be quite as low but additional cold weather advisories will likely be needed in higher terrain areas just from the bitter cold actual temperatures.

KEY MESSAGE 3...

We continue to monitor a robust winter storm tracking across the Southeast U.S and mid-Atlantic this weekend (mainly Sunday into Sunday night) with the latest guidance continuing to show two main scenarios. The first scenario shows the storm tracking further up the East Coast before sliding off the coast of NJ with its northern precipitation shield spreading into eastern NY and western New England. This would yield light to moderate snowfall amounts. Given how far south the sfc low remains even in this scenario, the highest precipitation and snowfall amounts look to be focused in areas mainly south of I-90 which is supported in the latest cluster analysis. The second scenario would keep the sfc low tracking well to our south and sliding off the coast of the Carolinas with high pressure remaining overhead keeping us mainly dry. However, even the clusters that favor this scenario shows light precipitation grazing our southern zones so it is unlikely that we remain completely dry.

The overall storm track will ultimately be dependent on if a trough digging into the Upper Plains this weekend ends up phasing with a southern stream shortwave coming in from the Desert Southwest. Should phasing occurs and the trough becomes more amplified, that would allow downstream ridging to build in the western Atlantic and help steer the storm further north. However, if phasing does not occur, the overall flow remains flatter and our winter storms likely escapes to our south.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Through 00z/Thu...High pressure south of the area will bring continued VFR conditions to the TAF sites through Wednesday morning. A clipper system approaches the area on Wednesday with increasing clouds and chances for light snow after 18z/Wed. The highest confidence in a period of light snow and possible IFR vsbys will be at KGFL with moderate confidence at KALB. Snow may stay to the west of KPSF and will stay well north of KPOU so these TAFs were kept dry. Wind will be southwesterly at 5-10 kt tonight then become southerly at around 10 kt on Wednesday with a few gusts to around 20 kt, especially at KALB.

Outlook...

Wednesday Night: Low Operational Impact. Slight Chance of SHSN. Thursday: Moderate Operational Impact. Windy With Gusts To 30 kts. Chance of SHSN. Thursday Night: Low Operational Impact. Breezy. NO SIG WX. Friday: Low Operational Impact. Breezy. NO SIG WX. Friday Night: Low Operational Impact. Breezy. NO SIG WX. Saturday: No Operational Impact. NO SIG WX. Saturday Night: Low Operational Impact. NO SIG WX. Sunday: Moderate Operational Impact. Chance of SHSN...SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Storm Warning until 7 AM EST Wednesday for NYZ032. Winter Storm Watch from Wednesday afternoon through Thursday afternoon for NYZ032-033-082. Winter Weather Advisory until 7 AM EST Wednesday for NYZ033. MA...None. VT...None.